Electrode-insulating means for spark plugs



Sept. 8, 1925.

W. S. THOMAS ELECTRODE INSULATING MEANS FOR SPARK PLUGS Filed Jan. 4. 1922 law/fs Patented Sept.i 8, y1925.V

UNITED. STATES PATENT WILLIAM s.V THOMAS, or RosELLE, NEW JERSEY, AssrGNoRmo THOMAS SPARK PLUG Yooit-intim, oE nosELLEA PARK, NEW JERSEY.

Appneenon alegria-eeft 4i, 19221 serieu szegse'e;

To all te hom it Be it known that Wimmer S. "inertes, e citizen ofthe United States, resid-ing et Roselle, in the county of Uonand State of Jersey, .have inyentedweertai'i new and useful Improvements' Ele=ctrode`1nsulating Means for Spark Plugs, o Which the following Ais a specification- One object of my present invention it to ioyide a spark plug electrode insulating structure 'including'l atube' so rilIgJ-ed ood p-roteotea that it will not te etree-ted' ty oils, gases or product-sof combustion and thus keep Vthe feite. tube in enen: oon'dit'io'p tlfezt it Will centir'lue during? the use of the plug to provide a practically perfectV electr-de insulator Another object is to' so construct and alrrerige my 'improved insulating means that it can be used advantageously in connection With various' forms' of spark plug structures and with practical advantage in connection With the structure of n'iy invention las covered" in my oo-pendngfa plica-tion for United Sta'tes"P`atent, Serial 1go; 480,913'.

These" objects, 'and other adyantageus ends which Will be described hereinafter,

I attain in' the following" manner, reference being had to'tlie accompanyinzg'f'7 dr'atfigsy in Which- Y Figure 1 is an elevation offa'n insulated electrode ineludingf Iny invention,

Figure 2y is' an enlarged longitudinal section of Figure 1,

Figure 3 is a section taken on the line 8-3 of Figure 2, andY l l Figures' 4, 5 and 64 are detail' sections showing various modifications of theiiisulting means. f

Referringtof Figures 1 tio 3 of thed'rawings, with the exception' of' the construction and arrangement of the mica' tube and its casing as Willl be more delinit'elyi described hereinafter', the structure is similarto that covered in In'y cof-pending" application for United States potent above mentioned and iti will be only necessary to aga-in' describe those parts which'v are essential to give a proper understanding of: the features of pjre'sentf invention.

An insulating core 8" which may be' made of any suitable electrode insulating material moieties@ body portion 9' what ie externally screw threaded at itstop as shown at`10.

A cap 11 `has internal screwtr threads 12 to alloW the cal'ilto be screwed on the body portion 9;v said -cz'p includes4 a chalnber 13 'positioned directly above Hthe top` of the body portion 9.'. This cap has radially disposed holesy Aor perfoi'aon's which ooinf inunicfate With the atiiiosphere and also with the chaniber' 13 allowing air to pass into and out of the chamber 13. The body 9 has anenlrged external' shoulder orV flange 15 which i s positionedY aboyeits lower end or nose 16. This flange 15 is usually provided on spark plug. electrode insulator bodies to effect the connection of the insulatorI body withV the" niet-allie jacket (not illustrated) to allow, they sparkV plug to be screwed intoV the cyli'n'd'enof an internel.v combustion engine. Furthermore the bodyv portion' a cylindrical cavity 17 extending axially d'owi'i'ward fronrtlie to'p surface 18' of the body portion 9. This c'ayity 17 terniinte's in a lower shoulder 19. A counter cayity 20, of sinaller diameter than' the cavity 17, leads downwardly from the steelt-lee 19 and' fome the top of e transversely extending Web 2 1; said Web being formed' integral with the other part of the core bod'y 9. A recessor cavity 22 entends upwardly and' axially from the bottoin surface 23 of the insulator nose 16 and the upper-"Wall ofthis recess 22 provides' the bottom of the Web 21.-

n" electrode Wire 25 lias'a' screu7 threaded `portion which eitelids through a' central hole 26 iny the'Web'214 ofthe insulator; al p'art of sid SorenA threaded portion of theele'ctrode Wire- 25 extending upwardly into the"` space provided by the cevit'y 17 .V Another' part of this screw threaded: portion of `the electrede` Wire extendsV belov tlie Web 2l and upon' this letter part of the eor'ett threaded 'portion of the electrode WireV is screwed a sinall nut 27l which" abut's the under surface of the Web 21. A second nut`28`- is screwed on the' upper portioiifof thewelectrode Wire and abutsthe'tojo su'rfa'c'e-v of the web 21' so thatr the web 21 Vis claiiiped between the nuts 27 and 28;

In accordance with my present invention I provide a mica tube 24 and enclose this n'wica tube in a casing 24 of glass, porcelain or other vitreous .material as clearly shown in Figures 2 and 3. The preferred manner of incasing said mica tube is to mold, coat or blow the vitreous material entirely around the mica tube so that there will be no portion of the mica exposed and the mica tube will be embedded entirely within the integral easing 24., This casing 24 of vitreous material fits the cavity 17; the lower edge of said casing resting on the shoulder 19. The internal diameter of the easing 24EL is such as to allow the electrode wire 25 to extend upwardly therein so as to be spaced from the inner surface of the casing as illustrated in Figures 2 and 3.

The casing 24a with the mica tube therein extends upwardly from the shoulder 19 which is below the flange to a position above the flange 15; said position preferably being coincident or flush with the upper surface 18 of the body portgion 9. The diameter of the electrode wire is small compared to the diameters of the counter cavity 20, recess 22 and internal diameter of the casing 24a so that there is a compara tively large air space present between the electrode wire and the inner surface of the casing 24a.

As illustrated the cap 11 has a metallic head 29 secured thereto and I have illustrated the head 29 including an enlarged flange 3() which abuts the uppermost surface of the chamber 13, and an angular portion 31 which may be embedded in the material of the cap so as to prevent rotation between the head 29 and the cap l1. The head 29 includes an upwardly extending screw' threaded stem 32 to which a thumb nut 33 is secured and I have also illustrated two other nuts Sel screwed on said stem and between these nuts and the thumb nut the usual electrode wire can be clamped. An electric conducting member 35 depends from the head 29 and I have illustrated this member in the form of a metallic tube which extends downwardly through the space within the casing 24a; said tube 35 being of smaller diameter than the internal diameter of the casing 24a so that there is an air space entirely surrounding the tube 35. The lower end of the metallic tube 35, when the cap 11 is screwed on the body portion 9, is adapted to vengage over the top portion of the electrode wire 25 and make electric connection therewith. The lower end of the tube 35 is slotted so as to make the same slightly resilient and capable of yielding so as to pass over the top of the electrode wire and then move into firm fitting engagement with the electrode wire.

It will be noted that the metallic members 25 and constitute an electrode which extends through the space provided by the internal diameter of the casing 24a and that the embedded mica tube 24 entirely sur rounds the electrode. Thus the iucased mica tube serves as a practically perfect insulator and guard against transverse current leakage or shortcircuiting. Thus with this construction I am enabled to increase to a very high degree the possibility of maintaining the dielectric strength of the insulator and to eliminate electrical leakage through conduction at or about the shoulder or thick portion 15 of the insulator and also at portions above and below said portion 15.

By incasing the mica it .is impossible to impair the insulating qualities thereof since oils, gases or products of combustion which may either pass upwardly or downwardly cannot engage the mica and hence will be kept in such condition as to advantageously serve as an insulator.

In Figure t, I have shown a construction in which the lower ,edge of the mica tube and the inner and outer si'de surfaces are covered by a vitreous case 21th and while this Structure is capable of protecting practically all of the mica tube the` same is not as desirable as that described in connection with Figures 1 to 3 inclusive, however, the same can be used in some instances. f

Figure 5 shows an arrangement where the upper and lower endsl as well as the inner surface of the mica tube are covered by a vitreous case 24@ and in Figure 6 I have shown a construction where the mica tube has its inner surface and lower edge covered by a vitreous ease 26W. In each instance the lower edge of the mica tube and the inner surface is protected so that the lower end of the case can rest upon the shoulder 19.

7h-ile I have described my invention as aking a particular form, it will be understood that the. various parts .of my invention may be changed without departing from the spirit thereof, and hence I do not limit myself to the precise construction set forth, but consider that I am at liberty to make such changes and alterations as fairly come within the scope of the appended claims.

Having thus described my invention7 what I claim as new and desire to secure by Letters Patent is 1- 1. Spark plug electrode insulating means including a mica tube entirely covered with vitreous material and spaced from the electrode; substantially as described.

2. Spark plug electrode insulating means including an insulating tube of high dielectric strength; an integral vitreous covering for the tube, said tube with its covering be ing spaced about the electrode, substantially as and for the purposes described.

3. Spark plug electrode insulating means including a mica tube embedded in a casing of vitreous material and spaced about the electrode, al1 portions of said casing being integral; substantially as described.

4. In a spa-rk plug; a body having a channel; an electrode extending through said channel; insulating means consisting of a mica tube surrounding the electrode but 

